1. Field of the Invention
The present invention relates generally to a method and apparatus for minimizing blurring of a captured image, and more particularly, to a method and apparatus for minimizing image blurring caused by motion of a subject.
2. Description of the Related Art
Devices for taking pictures of a subject may be classified into camcorders for capturing moving images and cameras for capturing still images. Recently, digital cameras that can capture both still and moving images have also been produced.
In imaging devices for picture taking, such as camcorders and digital cameras, light incident from a subject is converted and recorded by a photosensitive means such as an image sensor or film. The camera requires an exposure time during which a subject can be photo-sensed or exposed. Movement of a subject during the exposure time may result in a motion-blurred image.
As a solution for suppressing the motion blurring caused by motion of a subject, Panasonic Corporation (hereinafter, “Panasonic”) launched a LUMIX® digital camera with an intelligent ISO (International Standard Organization) function. The intelligent ISO function by Panasonic divides an image into four equal areas, compares each of the four areas with a corresponding same area in a previous image to calculate a motion, and applies the calculated motion to adjusting a shutter speed and ISO value (or light sensibility) of an image sensor.
In addition, Korean Patent Application No. 10-1995-0069717 filed by Samsung Electronics discloses a method for measuring a brightness of an initially taken image and then adjusting an iris size and a shutter speed based on the brightness to take a clearer image. Another conventional method includes detecting an entire motion of a background from a continuous image sequence received in a preview mode for previewing a captured image, and then executing a specific function of a camera according to motion of the camera.
The methods described above may be classified into two major types of methods. One such type of method includes combining a subject portion of a focused image with a small motion of the subject among multiple captured images, with a background of another image. The other such type of method includes measuring an illuminance of a subject or a background and adjusting an exposure condition like a shutter speed, and ISO value of an image sensor based on the illuminance measurement.
However, the method and apparatus proposed by Panasonic, which suppresses motion of a subject, requires a separate image stabilization device for suppressing blurring of a captured image due to hand vibration. Panasonic's method for preventing image blurring is not easily applied to a portable digital device that does not, or may not, include the image stabilization device.
However, the method of suppressing blurring caused by motion of a subject by measuring a brightness of the subject or a background and adjusting exposure conditions according to the brightness, does not suppress the image blurring caused by the motion of the subject when the opening time of a shutter is too long in view of a moving speed of the subject.
Images received in a Live View mode are dark and include many noises because resolution of Live View mode images is low and a flash cannot be used. Therefore, suppression of subject's motion is restricted, and quality of compensated images decreases. In addition, the Panasonic's method requiring a separate image stabilization device may not be easily applied in small portable communication terminals preferred by users.